On 05/12/2012 18:28, Shaun Thomas wrote:
Hey guys,
This isn't a question, but a kind of summary over a ton of investigation
I've been doing since a recent "upgrade". Anyone else out there with
"big iron" might want to confirm this, but it seems pretty reproducible.
This seems to affect the latest 3.2 mainline and by extension, any
platform using it. My tests are restricted to Ubuntu 12.04, but it may
apply elsewhere.
Very interesting results, I've been trying to benchmark my box but
getting what I would call poor performance given the setup, but I am
running 3.2 on ubuntu 12.04. Could I ask what hardware (offline if you
wish) was used for the results below?
Comparing the latest official 3.2 kernel to the latest official 3.4
kernel (both Ubuntu), there are some rather striking differences. I'll
start with some pgbench tests.
* This test is 800 read-only clients, with 2 controlling threads on a
55GB database (scaling factor of 3600) for 3 minutes.
* With 3.4:
* Max TPS was 68933.
* CPU was between 50 and 55% idle.
* Load average was between 10 and 15.
* With 3.2:
* Max TPS was 17583. A total loss of 75% performance.
* CPU was between 12 and 25% idle.
* Load average was between 10 and 60---effectively random.
* Next, we checked minimal write tests. This time, with only two
clients. All other metrics are the same.
* With 3.4:
* Max TPS was 4548.
* CPU was between 88 and 92% idle.
* Load average was between 1.7 and 2.5.
* With 3.2:
* Max TPS was 4639.
* CPU was between 88 and 92% idle.
* Load average was between 3 and 4.
TIme to see what a 3.4 kernel does to my setup I think?
Thanks
John
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